Councilmember Eric Ulrich voted against the resolution, because he believes speed cameras “are not proven to improve safety” and “will be used primarily as revenue generators for the city’s coffers.” Ulrich offered this as an alternative:

“I believe that greater traffic enforcement by the NYPD and installing traffic calming measures such as speed bumps and stop signs in speed prone locations is the best way to achieve this goal.”

Nobody disagrees that the NYPD could play a bigger role in keeping New York City’s streets safer, and while traffic calming certainly plays an important role in reducing vehicle speeds, not all traffic calming treatments are equal.

In fact, speed bumps and stop signs as traffic calming measures are an outdated approach — so outdated, in fact, that the NYCDOT Street Design Manual doesn’t even include them in its chapter on traffic calming. The problem is that they don’t produce the desired effect of calming traffic, or making vehicles move slowly. Instead, they require drivers to constantly change speeds, driving slowly just before they reach the speed bump or stop sign, and then accelerating in between to make up for lost time. This causes greater air — and noise — pollution, not to mention frustration, and there are few things more dangerous than a frustrated, speeding driver in New York City.

Modern alternatives to speed bumps like speed humps and speed tables (which are wider and more gradual than speed bumps) are better because vehicles driving at or below the speed limit aren’t forced to change speeds, but still, vertical devices in the roadway can present problems for snow plows and bicyclists. An even better approach is to design streets that cause vehicles to drive slowly by incorporating elements like street trees, curb extensions and narrower travel lanes.

Traffic calming measures must be implemented not only with sensitivity to the context of a given street and the surrounding neighborhood, but also with an understanding of how well certain measures reduce crashes on different types of streets. Any measure intended to change driver behavior is rated by what’s known as a “crash modification factor” (CMF) by the CMF Clearinghouse, the US Department of Transportation’s online repository of CMFs. The lower the CMF, the greater the ability to reduce the likelihood of crashes. For example, a traffic calming measure that has a CMF of .1 is very effective, reducing crashes by 90 percent, while a CMF of .9 is not as effective, reducing crashes by only 10 percent.

It’s not that stop signs or speed humps (the term “speed bumps” is not used in the CMF Clearinghouse) don’t significantly reduce crashes — they get a .6 and a .45, respectively — it’s that their application can only be limited to local roads. Stop signs and speed humps don’t make sense on arterial roads, which tend to be the most dangerous roads for pedestrians.

Speed cameras, on the other hand, could be installed on any type of roadway in the city. And on urban arterial roads (like Woodhaven Boulevard in Queens, Fourth Avenue in Brooklyn, or any of Manhattan’s avenues) speed cameras have a CMF of .46, that is, they reduce crashes by 54 percent.

Even media coverage of speed cameras has been shown to help reduce crashes — which suggests that drivers may drive more cautiously even in places where speed cameras are not installed, simply because they’ve heard that speed cameras have been installed.

“[S]peed reductions beyond the specific locations where cameras were deployed… is evidence that highly visible automated enforcement can promote community-wide changes in driver behavior. So-called “distance halo effects” are a key advantage of automated speed enforcement that generally are not achieved by traditional police speed enforcement… Increasing the perceived risk of detection is one of the most important objectives of all speed enforcement strategies.” (Evaluation of Automated Speed Enforcement in Montgomery County, Maryland)

8 comments to “Speed Bumps and Stop Signs” Are Not the Answer to Speeding in New York City

““Speed Bumps and Stop Signs” Are Not the Answer to Speeding in New York City” – Exactly right. Some of the best ways to reduce speed are two-way streets, allowing parking at rush hours, the near-eliimination of turn lanes and slip lanes, the narrowing of traffic lanes and the widening of sidewalks. Widening sidewalks is a better tool in cities than bumpouts, which work well on bad suburban streets. Their formulaic design in cities is usually bad placemaking and weak urban design, although they are good sometimes, of course.

One of the most effective tools is lowering speeds is… lowering speeds. A driver going 45 miles per hour (which is what New Yorkers drive in 35 mph zones) needs a lot of visual warning about when to turn, what obstacles might be on the road (like New York’s Copenhagen bike lanes, which need a lot of striping around them), and lots of signs that can be read at 45 mph. A driver going 25 miles per hours doesn’t need highway-scale stripings and signs because he has time to see the bicycle lane and react, and when al these warnings are gone, he has to pay more attention. And there’s the added benefit that getting rid of all the speed detritus makes more human-scaled places for the pedestrian.

““Speed Bumps and Stop Signs” Are Not the Answer to Speeding in New York City” – Exactly right. Some of the best ways to reduce speed are the use of two-way streets, allowing parking at rush hours, the near-eliimination of turn lanes and slip lanes, the narrowing of traffic lanes and the widening of sidewalks. Widening sidewalks is a better tool in cities than bumpouts, which work well on bad suburban streets. Their formulaic design in cities is usually bad placemaking and weak urban design, although they are good sometimes, of course.

One of the most effective tools in lowering speeds is… lowering speeds. A driver going 45 miles per hour (which is what New Yorkers drive in 35 mph zones) needs a lot of visual warning about when to turn, what obstacles might be on the road (like New York’s Copenhagen bike lanes, which need a lot of striping around them), and lots of signs that can be read at 45 mph. A driver going 25 miles per hours doesn’t need highway-scale stripings and signs because he has time to see the bicycle lane and react, and when al these warnings are gone, he has to pay more attention. And there’s the added benefit that getting rid of all the speed detritus makes more human-scaled places for the pedestrian.

[…] an even stronger case can be made for critical changes like better pedestrian crossings, traffic calming measures and enhanced speed enforcement strategies, while also advocating for infrastructure […]